title: Plant functional traits reveal the relative contribution of habitat and food preferences to the diet of grasshoppers.
abstract: Food preferences and food availability are two major determinants of the diet of generalist herbivores and of their spatial distribution. How do these factors interact and eventually lead to diet differentiation in co-occurring herbivores? We quantified the diet of four grasshopper species co-occurring in subalpine grasslands using DNA barcoding of the plants contained in the faeces of individuals sampled in the field. The food preferences of each grasshopper species were assessed by a choice (cafeteria) experiment from among 24 plant species common in five grassland plots, in which the four grasshoppers were collected, while the habitat was described by the relative abundance of plant species in the grassland plots. Plant species were characterised by their leaf economics spectrum (LES), quantifying their nutrient vs. structural tissue content. The grasshoppers' diet, described by the mean LES of the plants eaten, could be explained by their plant preferences but not by the available plants in their habitat. The diet differed significantly across four grasshopper species pairs out of six, which validates food preferences assessed in standardised conditions as indicators for diet partitioning in nature. In contrast, variation of the functional diversity (FD) for LES in the diet was mostly correlated to the FD of the available plants in the habitat, suggesting that diet mixing depends on the environment and is not an intrinsic property of the grasshopper species. This study sheds light on the mechanisms determining the feeding niche of herbivores, showing that food preferences influence niche position whereas habitat diversity affects niche breadth.
authors.affiliation: Community Ecology Research Unit, Swiss Federal Research Institute WSL, Via Belsoggiorno 22, 6500, Bellinzona, Switzerland, sebastien.ibanez@univ-savoie.fr.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Ibanez
authors.forename: Olivier
authors.initials: O
authors.lastname: Manneville
authors.forename: Christian
authors.initials: C
authors.lastname: Miquel
authors.forename: Pierre
authors.initials: P
authors.lastname: Taberlet
authors.forename: Alice
authors.initials: A
authors.lastname: Valentini
authors.forename: Serge
authors.initials: S
authors.lastname: Aubert
authors.forename: Eric
authors.initials: E
authors.lastname: Coissac
authors.forename: Marie-Pascale
authors.initials: MP
authors.lastname: Colace
authors.forename: Quentin
authors.initials: Q
authors.lastname: Duparc
authors.forename: Sandra
authors.initials: S
authors.lastname: Lavorel
authors.forename: Marco
authors.initials: M
authors.lastname: Moretti
mesh_terms: D000818:Animals; D058893:DNA Barcoding, Taxonomic; D004032:Diet; D017753:Ecosystem; D005260:Female; D005518:Food Preferences; D006110:Grasshoppers; D060434:Herbivory; D008297:Male; D010944:Plants / Q000145:classification*